Recently, there are provided methods, mainly adapted to multicarrier transmission systems, in which a plurality of blocks are divided along frequency and time axes and which perform scheduling on signals transmitted to users from wireless transmission devices in units of blocks. Herein, regions that are secured for users to perform communications and that are defined along the frequency and time axes are referred to as assignment slots, and blocks serving as the basis for determining assignment slots are referred to as chunks.
In the above, there are provided methods that, in order to transmit broadcast signals, multicast signals, and control signals, blocks whose ranges are broadened in the frequency axis direction are assigned so as to produce frequency diversity effects, thus reducing errors irrespective of low reception power. In addition, there are provided methods that, in order to transmit unicast signals in one-to-one communications between wireless transmission devices and wireless reception devices, blocks whose ranges are reduced in the frequency axis direction are assigned so as to produce multiuser diversity effects, thus improving reception power in wireless reception devices.
FIGS. 16A and 16B show the relationships regarding signals transmitted from a wireless transmission device to a wireless reception device with respect to time (horizontal axis) and frequency (vertical axis). In FIG. 16A, the horizontal axis represents time, and the vertical axis represents frequency. Transmission times t1 to t3 are set to the time axis. Herein, the same time length is set to the times t1 to t3 respectively. Transmission frequencies f1 to f5 are set to the frequency axis. Herein, a same frequency range Fc is set to the frequencies f1 to f5. With reference to the transmission times t1 to t3 and the transmission frequencies f1 to f5, fifteen chunks K1 to K15 are set as shown in FIG. 16A.
Furthermore, five chunks K1 to K5 are connected as shown in FIG. 16B and are then equally divided into six slots along the time axis, thus setting communication slots s1 to s6 each of which has a time length of t1/6 and a frequency range of 5f1. The communication slots s1 and s4 are assigned to a first user; the communication slots s2 and s5 are assigned to a second user; and the communication slots s3 and s6 are assigned to a third user. This makes it possible for the first to third users to obtain frequency diversity effects.
Next, the chunk K10 is assigned to a fourth user as a communication slot s11. The chunks K7, K8, and K9 are connected so as to form communication slots s8 to s10, each of which has a time length of t2 and a frequency range of 3f1 and which are assigned to a fifth user. Furthermore, the chunk K6 is assigned to a sixth user as a communication slot s7. This makes it possible for the fourth to sixth users to obtain multiuser diversity effects, and this makes it possible for the fifth user to obtain a frequency diversity effect.
Furthermore, the chunk K11 is assigned to a seventh user as a communication slot s12. This makes it possible for this user to obtain a multiuser diversity effect. Furthermore, the chunks K13 and K15 are assigned to an eighth user as communication slots s19 and s26. This makes it possible for this user to obtain a multiuser diversity effect.
Furthermore, the two chunks K12 and K14 are equally divided into six slots, thus forming slots s13 to s18 and s20 to s25. The communication slots s13, s16, s20, and s23 are assigned to a ninth user; the communication slots s14, s17, s21, and s24 are assigned to a tenth user; and the communication slots s15, s18, s22, and s25 are assigned to an eleventh user. This makes it possible for the ninth to eleventh users to obtain frequency diversity effects individually.
Non-patent document 1: Contribution to 3GPP, R1-050249, “Downlink Multiple Access Scheme for Evolved UTRA”, [Retrieval on Aug. 17, 2005], Internet (URL: ftp://ftp.3gpp.org/TSG_RAN/WG1_RL1/TSGR1—40bis/Docs/R1-050249.zip)
Non-patent document 2: Contribution to 3GPP, R1-050590, “Physical Channels and Multiplexing in Evolved UTRA Downlink”, [Retrieval on Aug. 17, 2005], Internet (URL: ftp://ftp.3gpp.org/TSG_RAN/WG1_RL1/R1_Ad_Hocs/LTE_AH_June-05/Docs/R1-050590.zip)